#include <iostream>
const int LARGE_NUMBER = 1000000007;
const int size = 3001;
int fracs[size][size] = {0,};
template<int LN>
struct fraction
{
int mod;
fraction() : mod(0) {}
fraction(int _denom, int _num)
{
if( _denom < size && _num < size && fracs[_denom][_num] )
{
mod = fracs[_denom][_num];
}
else
{
mod = getmod(_denom,_num);
if( _denom < size && _num < size )
fracs[_denom][_num] = mod;
}
}
int modpow( long long A, long long X )
{
int acc = 1;
while(X)
{
A %= LN;
if(X%2)
acc = (A*acc)%LN;
A = A*A;
X /= 2;
}
return acc;
}
int getmod( int denom, int num )
{
int rev = modpow(denom, LN-2);
int mod = ((long long)num*rev)%LN;
return mod;
}
fraction operator+( const fraction& op )
{
return fraction((this->mod+op.mod)%LN);
}
fraction operator-( const fraction& op )
{
return fraction((this->mod-op.mod+LN)%LN);
}
fraction operator*( const fraction& op )
{
return fraction(((long long)(this->mod)*op.mod)%LN);
}
fraction operator/( const fraction& op )
{
return fraction(op.mod, this->mod);
}
private:
fraction(int _mod) : mod(_mod) {}
};
typedef fraction<LARGE_NUMBER> frac;
int N, L;
frac probs[size][size];
frac calc_prob( int remain_D, int remain_L )
{
if( probs[remain_D][remain_L].mod != -1 )
return probs[remain_D][remain_L];
if( remain_D > remain_L )
return frac();
frac p1 = calc_prob(remain_D, remain_L-1) * frac(N, N-remain_D);
frac p2 = calc_prob(remain_D-1, remain_L-1) * frac(N, remain_D);
probs[remain_D][remain_L] = p1+p2;
return probs[remain_D][remain_L];
}
int main()
{
probs[0][0].mod = 1;
for( int i = 1; i < size; ++i )
{
probs[i][0].mod = 0;
probs[0][i].mod = 1;
}
while( std::cin >> N >> L )
{
for( int i = 1; i <= N; ++i ) for( int j = 1; j <= L; ++j ) probs[i][j].mod = -1;
int remain_D = 0;
for( int i = 0; i < N; ++i )
{
int D;
std::cin >> D;
if( D == 1 )
++remain_D;
}
frac prob = calc_prob( remain_D, L );
std::cout << prob.mod << std::endl;
}
return 0;
}
